Iran's new ultra-conservative President Mahmoud Ahmadinejad has been confirmed in office, following his surprise election victory in July.

His endorsement came as Tehran said it hoped to restart its controversial nuclear activities on Wednesday.

One of his first challenges will be a row with the US and EU, which want an end to Iran's nuclear programme.

The former mayor of Tehran succeeds reformist Mohammad Khatami, who leaves office after eight years in power.

Following his endorsement by Iran's supreme leader Ayatollah Ali Khamenei, 49-year-old President Ahmadinejad said he will lobby for the elimination of weapons of mass destruction around the world and for international justice.

Nuclear row

With Mr Ahmadinejad in power it means an end to the reform period in Iran - hardliners now control all the institutions of power, says the BBC's Frances Harrison in Tehran.

But our correspondent says he inherits what looks set to be a major foreign policy crisis, triggered by Iran's decision this week to resume conversion of uranium.

A spokesman for Iran's Supreme National Security Council said a request by the UN's nuclear watchdog to wait a week to allow surveillance systems to be installed was unacceptable.